Seaweeds as Nutraceutical Elements and Drugs for Diabetes Mellitus: Future Perspectives.

Diabetes mellitus is a chronic metabolic condition marked by high blood glucose levels caused by inadequate insulin synthesis or poor insulin use. This condition affects millions of individuals worldwide and is linked to a variety of consequences, including cardiovascular disease, neuropathy, nephropathy, and retinopathy. Diabetes therapy now focuses on controlling blood glucose levels through lifestyle changes, oral medicines, and insulin injections. However, these therapies have limits and may not successfully prevent or treat diabetic problems. Several marine-derived chemicals have previously demonstrated promising findings as possible antidiabetic medicines in preclinical investigations. Peptides, polyphenols, and polysaccharides extracted from seaweeds, sponges, and other marine species are among them. As a result, marine natural products have the potential to be a rich source of innovative multitargeted medications for diabetes prevention and treatment, as well as associated complications. Future research should focus on the chemical variety of marine creatures as well as the mechanisms of action of marine-derived chemicals in order to find new antidiabetic medicines and maximize their therapeutic potential. Based on preclinical investigations, this review focuses on the next step for seaweed applications as potential multitargeted medicines for diabetes, highlighting the bioactivities of seaweeds in the prevention and treatment of this illness.

Ecotoxicological Effects of the Anionic Surfactant Sodium Dodecyl Sulfate (SDS) in Two Marine Primary Producers: Phaeodactylum tricornutum and Ulva lactuca.

Sodium Dodecyl Sulfate (SDS) is an anionic surfactant, extensively used in detergents, household and personal care products, as well as in industrial processes. The present study aimed to disclose the potential toxicological effects of SDS exposure under environmentally relevant concentrations (0, 0.1, 1, 3, and 10 mg L-1) on the physiology and biochemistry (photosynthesis, pigment, and lipid composition, antioxidative systems, and energy balance) of two marine autotrophs: the diatom Phaeodactylum tricornutum and the macroalgae Ulva lactuca. A growth rate (GR) reduction in P. tricornutum was observed with a classic dose-response effect towards the highest applied concentration, while a GR increase occurred in U. lactuca. Regarding photochemistry, the decrease in the fluorescence of the OJIP curves and laser-induced fluorescence allowed a better separation between SDS treatments in U. lactuca compared with P. tricornutum. Although all pigments significantly decreased in U. lactuca at the highest concentrations (except for antheraxanthin), no significant variations occurred in P. tricornutum. On the other hand, changes in fatty acid content were observed in P. tricornutum but not in U. lactuca. In terms of classical biomarker assessment, a dose-effect relationship of individual biomarkers versus SDS dose applied; U. lactuca displayed a higher number of biomarker candidates, including those in distinct metabolic pathways, increasing its usefulness for ecotoxicological applications. By evaluating the potential application of optical and biochemical traits, it was evident that the fatty acid profiles of the different exposure groups are excellent candidates in P. tricornutum, concomitant with the characteristics of this anionic surfactant. On the other hand, the results presented by laser-induced fluorescence and some parameters of PAM fluorometry in U. lactuca may be an advantage in the field, offering non-invasive, fast, easy-to-use, high-throughput screening techniques as excellent tools for ecotoxicology assessment.

Boom and bust: Simulating the effects of climate change on the population dynamics of a global invader near the edge of its native range.

Despite the increasing awareness of climate change, few studies have used the Intergovernmental Panel on Climate Change (IPCC) scenarios to simulate the effects of climate change on estuarine populations of crustaceans. The objective of this study was to investigate the effects of temperature and salinity fluctuations on the population dynamics of the shore crab Carcinus maenas at the southern edge of its native range. To this end, a population dynamics model was developed based on experimental and literature data on the biology, ecology and physiology of the species. Results showed that the shore crab will be more affected by changes in temperature than in salinity. The parameter sensitivity analysis revealed that the larval phase of the species is the most sensitive stage of the shore crab life cycle. Three IPCC scenarios (SSP1-2.6, SSP2-4.5, and SSP3-8.5) were used to simulate the effects of temperature increase on the population of C. maenas in the near- (2040), mid- (2060), and long-term (2100). Two scenarios of drought conditions accompanied by the estimated salinity change were also simulated (10 % and 40 % drought). Results suggested that slight increases in temperature (up to 2 °C) lead to a strong increase on the density of C. maenas in the mid-term, while further temperature increases lead to a decline or local extinction of the shore crab population at the southern edge of its distribution range. Results indicated that a salinity increase in the estuary had a negative effect on the shore crab population. Given the importance of the species to temperate coastal ecosystems, both population increase and local extinction are likely to have significant impacts on estuarine communities and food webs, with unknown ecological and socioeconomic consequences.

Effects of Glyphosate-Based Herbicide on Primary Production and Physiological Fitness of the Macroalgae Ulva lactuca.

The use of glyphosate-based herbicides (GBHs) worldwide has increased exponentially over the last two decades increasing the environmental risk to marine and coastal habitats. The present study investigated the effects of GBHs at environmentally relevant concentrations (0, 10, 50, 100, 250, and 500 µg·L-1) on the physiology and biochemistry (photosynthesis, pigment, and lipid composition, antioxidative systems and energy balance) of Ulva lactuca, a cosmopolitan marine macroalgae species. Although GBHs cause deleterious effects such as the inhibition of photosynthetic activity, particularly at 250 µg·L-1, due to the impairment of the electron transport in the chloroplasts, these changes are almost completely reverted at the highest concentration (500 µg·L-1). This could be related to the induction of tolerance mechanisms at a certain threshold or tipping point. While no changes occurred in the energy balance, an increase in the pigment antheraxanthin is observed jointly with an increase in ascorbate peroxidase activity. These mechanisms might have contributed to protecting thylakoids against excess radiation and the increase in reactive oxygen species, associated with stress conditions, as no increase in lipid peroxidation products was observed. Furthermore, changes in the fatty acids profile, usually attributed to the induction of plant stress response mechanisms, demonstrated the high resilience of this macroalgae. Notably, the application of bio-optical tools in ecotoxicology, such as pulse amplitude modulated (PAM) fluorometry and laser-induced fluorescence (LIF), allowed separation of the control samples and those treated by GBHs in different concentrations with a high degree of accuracy, with PAM more accurate in identifying the different treatments.

Effect Biomarkers of the Widespread Antimicrobial Triclosan in a Marine Model Diatom.

The present-day COVID-19 pandemic has led to the increasing daily use of antimicrobials worldwide. Triclosan is a manmade disinfectant chemical used in several consumer healthcare products, and thus frequently detected in surface waters. In the present work, we aimed to evaluate the effect of triclosan on diatom cell photophysiology, fatty acid profiles, and oxidative stress biomarkers, using the diatom Phaeodactylum tricornutum as a model organism. Several photochemical effects were observed, such as the lower ability of the photosystems to efficiently trap light energy. A severe depletion of fucoxanthin under triclosan application was also evident, pointing to potential use of carotenoid as reactive oxygen species scavengers. It was also observed an evident favouring of the peroxidase activity to detriment of the SOD activity, indicating that superoxide anion is not efficiently metabolized. High triclosan exposure induced high cellular energy allocation, directly linked with an increase in the energy assigned to vital functions, enabling cells to maintain the growth rates upon triclosan exposure. Oxidative stress traits were found to be the most efficient biomarkers as promising tools for triclosan ecotoxicological assessments. Overall, the increasing use of triclosan will lead to significant effects on the diatom photochemical and oxidative stress levels, compromising key roles of diatoms in the marine system.

Impacts of low concentrations of nanoplastics on leaf litter decomposition and food quality for detritivores in streams.

In forested streams, leaf litter decomposition is a vital ecosystem process, governed primarily by aquatic hyphomycetes. These fungi are crucial mediators of nutrients and energy to invertebrates and higher trophic levels. Very little information is available on the impact of low concentrations of different sizes of nanoplastic particles (NPPs) on leaf litter decomposition and aquatic hyphomycetes communities. Besides, NPPs impact on leaf litter nutritional quality and invertebrate feeding behaviour is unknown. We conducted a microcosm assay with varying concentrations (0-25 µg L-1) of small (100 nm; SNPPs) and large (1000 nm; LNPPs) plastic particles to assess their impact on leaf litter decomposition, sporulation rates and community structure of aquatic hyphomycetes. Furthermore, leaf litter was retrieved and fed to invertebrates to assess feeding rates. Our results indicated that leaf litter decomposition, fungal sporulation and abundance were significantly affected by NPPs concentrations and sizes. By contrast, leaf litter nutritional quality was impacted only by sizes. The NPPs, particularly SNPPs, augmented leaf litter polyunsaturated fatty acids (18-31%), consequently improving food quality; however, invertebrates' feeding rates were not impacted. Overall, our study provides novel insights on the risks posed by NPPs with pronounced impact at the basal trophic level.

Trace element bioaccumulation in hypersaline ecosystems and implications of a global invasion.

Hypersaline ecosystems are under increasing threat due to anthropogenic pressures such as environmental pollution and biological invasions. Here we address the ecotoxicological implications of the Artemia franciscana (Crustacea) invasion in saltpans of southern Spain. This North American species is causing the extinction of native Artemia populations in many parts of the globe. The bioaccumulation of trace elements (As, Cd, Cu, Co, Cr, Mn, Ni, Pb and Zn) in native populations (A. parthenogenetica) from Cabo de Gata and Odiel saltpans and invasive Artemia from Cádiz saltpan was studied at different salinities. Furthermore, in Odiel, the most polluted study site, we also analysed the bioaccumulation of trace elements by Chironomus salinarius larvae (Diptera) and Ochthebius notabilis adults (Coleoptera). High levels of trace elements were detected in the studied saltpans, many of them exceeding the recommended threshold guidelines for aquatic life. Bioaccumulation of trace elements by Artemia was lowest at the highest salinity. The invasive A. franciscana showed higher potential to bioaccumulate trace elements than its native counterpart (in particular for As, Cd, Ni and Cr). In Odiel, O. notabilis stood out as showing the highest potential to bioaccumulate As and Cu. Results showed that the shift from a native to an alien Artemia species with a higher bioaccumulation capacity may increase the transfer of trace elements in hypersaline food webs, especially for waterbirds that depend on Artemia as food. Thus, our study identifies an indirect impact of the Artemia franciscana invasion that had not previously been recognised.

An Overview to the Health Benefits of Seaweeds Consumption.

Currently, seaweeds are gaining major attention due to the benefits they give to our health. Recent studies demonstrate the high nutritional value of seaweeds and the powerful properties that seaweeds' bioactive compounds provide. Species of class Phaeophyceae, phylum Rhodophyta and Chlorophyta possess unique compounds with several properties that are potential allies of our health, which make them valuable compounds to be involved in biotechnological applications. In this review, the health benefits given by consumption of seaweeds as whole food or by assumption of bioactive compounds trough natural drugs are highlighted. The use of seaweeds in agriculture is also highlighted, as they assure soils and crops free from chemicals; thus, it is advantageous for our health. The addition of seaweed extracts in food, nutraceutical, pharmaceutical and industrial companies will enhance the production and consumption/usage of seaweed-based products. Therefore, there is the need to implement the research on seaweeds, with the aim to identify more bioactive compounds, which may assure benefits to human and animal health.

Environmental Impact on Seaweed Phenolic Production and Activity: An Important Step for Compound Exploitation.

Seaweeds are a potential source of bioactive compounds that are useful for biotechnological applications and can be employed in different industrial areas in order to replace synthetic compounds with components of natural origin. Diverse studies demonstrate that there is a solid ground for the exploitation of seaweed bioactive compounds in order to prevent illness and to ensure a better and healthier lifestyle. Among the bioactive algal molecules, phenolic compounds are produced as secondary metabolites with beneficial effects on plants, and also on human beings and animals, due to their inherent bioactive properties, which exert antioxidant, antiviral, and antimicrobial activities. The use of phenolic compounds in pharmaceutical, nutraceutical, cosmetics, and food industries may provide outcomes that could enhance human health. Through the production of healthy foods and natural drugs, bioactive compounds from seaweeds can help with the treatment of human diseases. This review aims to highlight the importance of phenolic compounds from seaweeds, the scope of their production in nature and the impact that these compounds can have on human and animal health through nutraceutical and pharmaceutical products.

Effects of Propranolol on Growth, Lipids and Energy Metabolism and Oxidative Stress Response of Phaeodactylum tricornutum.

Present demographic trends suggest a rise in the contributions of human pharmaceuticals into coastal ecosystems, underpinning an increasing demand to evaluate the ecotoxicological effects and implications of drug residues in marine risk assessments. Propranolol, a non-selective ß-adrenoceptor blocker, is used worldwide to treat high blood pressure conditions and other related cardiovascular conditions. Although diatoms lack ß-adrenoceptors, this microalgal group presents receptor-like kinases and proteins with a functional analogy to the animal receptors and that can be targeted by propranolol. In the present work, the authors evaluated the effect of this non-selective ß-adrenoceptor blocker in diatom cells using P. tricornutum as a model organism, to evaluate the potential effect of this compound in cell physiology (growth, lipids and energy metabolism and oxidative stress) and its potential relevance for marine ecosystems. Propranolol exposure leads to a significant reduction in diatom cell growth, more evident in the highest concentrations tested. This is likely due to the observed impairment of the main primary photochemistry processes and the enhancement of the mitochondrial respiratory activity. More specifically, propranolol decreased the energy transduction from photosystem II (PSII) to the electron transport chain, leading to an increase in oxidative stress levels. Cells exposed to propranolol also exhibited high-dissipated energy flux, indicating that this excessive energy is efficiently diverted, to some extent, from the photosystems, acting to prevent irreversible photoinhibition. As energy production is impaired at the PSII donor side, preventing energy production through the electron transport chain, diatoms appear to be consuming storage lipids as an energy backup system, to maintain essential cellular functions. This consumption will be attained by an increase in respiratory activity. Considering the primary oxygen production and consumption pathways, propranolol showed a significant reduction of the autotrophic O2 production and an increase in the heterotrophic mitochondrial respiration. Both mechanisms can have negative effects on marine trophic webs, due to a decrease in the energetic input from marine primary producers and a simultaneous oxygen production decrease for heterotrophic species. In ecotoxicological terms, bio-optical and fatty acid data appear as highly efficient tools for ecotoxicity assessment, with an overall high degree of classification when these traits are used to build a toxicological profile, instead of individually assessed.

Thermodynamics in Ecology-An Introductory Review.

How to predict the evolution of ecosystems is one of the numerous questions asked of ecologists by managers and politicians. To answer this we will need to give a scientific definition to concepts like sustainability, integrity, resilience and ecosystem health. This is not an easy task, as modern ecosystem theory exemplifies. Ecosystems show a high degree of complexity, based upon a high number of compartments, interactions and regulations. The last two decades have offered proposals for interpretation of ecosystems within a framework of thermodynamics. The entrance point of such an understanding of ecosystems was delivered more than 50 years ago through Schrödinger's and Prigogine's interpretations of living systems as "negentropy feeders" and "dissipative structures", respectively. Combining these views from the far from equilibrium thermodynamics to traditional classical thermodynamics, and ecology is obviously not going to happen without problems. There seems little reason to doubt that far from equilibrium systems, such as organisms or ecosystems, also have to obey fundamental physical principles such as mass conservation, first and second law of thermodynamics. Both have been applied in ecology since the 1950s and lately the concepts of exergy and entropy have been introduced. Exergy has recently been proposed, from several directions, as a useful indicator of the state, structure and function of the ecosystem. The proposals take two main directions, one concerned with the exergy stored in the ecosystem, the other with the exergy degraded and entropy formation. The implementation of exergy in ecology has often been explained as a translation of the Darwinian principle of "survival of the fittest" into thermodynamics. The fittest ecosystem, being the one able to use and store fluxes of energy and materials in the most efficient manner. The major problem in the transfer to ecology is that thermodynamic properties can only be calculated and not measured. Most of the supportive evidence comes from aquatic ecosystems. Results show that natural and culturally induced changes in the ecosystems, are accompanied by a variations in exergy. In brief, ecological succession is followed by an increase of exergy. This paper aims to describe the state-of-the-art in implementation of thermodynamics into ecology. This includes a brief outline of the history and the derivation of the thermodynamic functions used today. Examples of applications and results achieved up to now are given, and the importance to management laid out. Some suggestions for essential future research agendas of issues that needs resolution are given.

Comfortably numb: Ecotoxicity of the non-steroidal anti-inflammatory drug ibuprofen on Phaeodactylum tricornutum.

Emerging pollutants such as pharmaceuticals are continuously released to aquatic environments posing a rising threat to marine ecosystems. Yet, monitoring routines and ecotoxicity data on biota worldwide for these substances are lacking. Non-steroidal anti-inflammatory drugs are among the most prescribed and found pharmaceuticals in aquatic environments. The toxicity effects of environmentally relevant concentrations of ibuprofen on primary productivity, oxidative stress and lipid metabolism of the diatom Phaeodactylum tricornutum were assessed. Diatom cultures were exposed to 0, 0.8, 3, 40, 100 and 300 µg L-1 ibuprofen concentrations, usually found in the vicinity of wastewater treatment plants and coastal environments. Higher concentrations (100 and 300 µg L-1) had a negative impact in P. triconutum growth, inhibiting the chloroplastic energy transduction in the electron transport chain resulting in lower energy reaching the PS I (r2 = -0.55, p < 0.05). In contrast, the mitochondrial electron transport and available energy increased (r2 = 0.68 and r2 = 0.85, p < 0.05 respectively), mostly due to enhancements in lipid and protein contents as opposed to reduction of carbohydrates. A general up-regulation of the antioxidant enzymes could contributed to alleviate oxidative stress resulting in the decrease of lipid peroxidation products (r2 = 0.77, p < 0.05). Canonical analysis of principal components was performed and successfully discriminated exposure groups, with optical data excelling in classifying samples to different ibuprofen concentrations, being potentially used as environmental indicators. Finally, the identified mild to severe effects of ibuprofen on diatoms are likely to be exacerbated by the sustained use of this drug worldwide, underpinning the urgency of evaluating the impacts of this pharmaceutical on coastal and marine trophic webs.

Fluoxetine Arrests Growth of the Model Diatom Phaeodactylum tricornutum by Increasing Oxidative Stress and Altering Energetic and Lipid Metabolism.

Pharmaceutical residues impose a new and emerging threat to aquatic environments and its biota. One of the most commonly prescribed pharmaceuticals is the antidepressant fluoxetine, a selective serotonin re-uptake inhibitor that has been frequently detected, in concentrations up to 40 µg L-1, in aquatic ecosystems. The present study aims to investigate the ecotoxicity of fluoxetine at environmentally relevant concentrations (0.3, 0.6, 20, 40, and 80 µg L-1) on cell energy and lipid metabolism, as well as oxidative stress biomarkers in the model diatom Phaeodactylum tricornutum. Exposure to higher concentrations of fluoxetine negatively affected cell density and photosynthesis through a decrease in the active PSII reaction centers. Stress response mechanisms, like ß-carotene (ß-car) production and antioxidant enzymes [superoxide dismutase (SOD) and ascorbate peroxidase (APX)] up-regulation were triggered, likely as a positive feedback mechanism toward formation of fluoxetine-induced reactive oxygen species. Lipid peroxidation products increased greatly at the highest fluoxetine concentration whereas no variation in the relative amounts of long chain polyunsaturated fatty acids (LC-PUFAs) was observed. However, monogalactosyldiacylglycerol-characteristic fatty acids such as C16:2 and C16:3 increased, suggesting an interaction between light harvesting pigments, lipid environment, and photosynthesis stabilization. Using a canonical multivariate analysis, it was possible to evaluate the efficiency of the application of bio-optical and biochemical techniques as potential fluoxetine exposure biomarkers in P. tricornutum. An overall classification efficiency to the different levels of fluoxetine exposure of 61.1 and 88.9% were obtained for bio-optical and fatty acids profiles, respectively, with different resolution degrees highlighting these parameters as potential efficient biomarkers. Additionally, the negative impact of this pharmaceutical molecule on the primary productivity is also evident alongside with an increase in respiratory oxygen consumption. From the ecological point of view, reduction in diatom biomass due to continued exposure to fluoxetine may severely impact estuarine and coastal trophic webs, by both a reduction in oxygen primary productivity and reduced availability of key fatty acids to the dependent heterotrophic upper levels.

Life history and physiological responses of native and invasive brine shrimps exposed to zinc.

Although a substantial amount of research exists on pollution and biological invasions, there is a paucity of understanding of how both factors interact. Most studies show that pollution favours the establishment of invasive species, but pollution may also promote local adaptation of native species and prevent the establishment of new incomers. However, evidence for this is extremely limited because most studies focus on successful invasions and very few on cases where an invasion has been resisted. Here we provide evidence of local adaptation of native species to pollution combining life history and physiological data. We focused on the invasion of the North American brine shrimp Artemia franciscana, which is causing a dramatic biodiversity loss in hypersaline ecosystems worldwide, and one of the last native Artemia populations in SW Europe (A. parthenogenetica from the historically polluted Odiel estuary, SW Spain). Life table response experiments were carried out in the laboratory to compare the demographic responses of A. parthenogenetica and a nearby A. franciscana population to long-term Zn exposure (0.2 mg L-1). We also evaluated oxidative stress by measuring antioxidant defences (catalase, glutathione reductase and superoxide dismutase) and lipid peroxidation (thiobarbituric acid reactive substances). A high concentration of Zn induced strong mortality in A. franciscana, which also showed high levels of lipid peroxidation, suggesting relatively poor physiological resistance to pollution compared with A. parthenogenetica. The age at maturity was shorter in A. parthenogenetica, which may be an adaptation to the naturally high mortality rate observed in the Odiel population. Exposure to Zn accelerated age at first reproduction in A. franciscana but not in A. parthenogenetica. In contrast, Zn had a stimulatory effect on offspring production in A. parthenogenetica,which also showed higher reproductive parameters (number of broods, total offspring and offspring per brood) than A. franciscana. Overall, the results of this study strongly suggest that native Artemia from Odiel estuary is locally adapted (at both, reproductive and physiological levels) to Zn contamination and that A. franciscana is highly sensitive. This is a good example of how pollution may play a role in the persistence of the last native Artemia populations in the Mediterranean.

Ecotoxicity of the lipid-lowering drug bezafibrate on the bioenergetics and lipid metabolism of the diatom Phaeodactylum tricornutum.

Pharmaceutical residues impose a new and emerging threat to the marine environment and its biota. In most countries, ecotoxicity tests are not required for all pharmaceutical residues classes and, even when mandatory, these tests are not performed using marine primary producers such as diatoms. These microalgae are among the most abundant class of primary producers in the marine realm and key players in the marine trophic web. Blood-lipid-lowering agents such as bezafibrate and its derivatives are among the most prescribed drugs and most frequently found human pharmaceuticals in aquatic environments. The present study aims to investigate the bezafibrate ecotoxicity and its effects on primary productivity and lipid metabolism, at environmentally relevant concentrations, using the model diatom Phaeodactylum tricornutum. Under controlled conditions, diatom cultures were exposed to bezafibrate at 0, 3, 6, 30 and 60 µg L-1, representing concentrations that can be found in the vicinity of discharges of wastewater treatment plants. High bezafibrate concentrations increased cell density and are suggested to promote a shift from autotrophic to mixotrophic metabolism, with diatoms using light energy generated redox potential to breakdown bezafibrate as carbon source. This was supported by an evident increase in cell density coupled with an impairment of the thylakoid electron transport and consequent photosynthetic activity reduction. In agreement, the concentrations of plastidial marker fatty acids showed negative correlations and Canonical Analysis of Principal coordinates of the relative abundances of fatty acid and photochemical data allowed the separation of controls and cells exposed to bezafibrate with high classification efficiency, namely for photochemical traits, suggesting their validity as suitable biomarkers of bezafibrate exposure. Further evaluations of the occurrence of a metabolic shift in diatoms due to exposure to bezafibrate is paramount, as ultimately it may reduce O2 generation and CO2 fixation in aquatic ecosystems with ensuing consequences for neighboring heterotrophic organisms.

Assessing the effects of temperature and salinity oscillations on a key mesopredator fish from European coastal systems.

A population dynamics model was developed to assess the short and long-term effects of temperature and salinity variations in the common goby Pomatoschistus microps in a Portuguese estuary (Minho estuary, NW Portugal). The population was divided into juveniles, females and males, which constituted the model's state variables. Linear regressions between the observed and the predicted density of juveniles, females and the total population were significant. Parameter's sensitivity and uncertainty analysis were estimated. The model was able to satisfactory describe the P. microps population dynamics, and thus was used to simulate the effects of climatic changes on the fish population. Simulations indicated that the common goby population is sensitive to both temperature and salinity changes. Overall, scenarios of more than 3 °C increase caused significant population decreases. Similarly, increased salinities led to a population shrinkage, whereas scenarios of salinity decrease generated an opposite variation on the population. According to the IPCC predictions for climatic tendencies, the population of the common goby will tend to decrease in the near future, experiencing marked oscillations (decrease or increase) during climatic extremes, namely droughts and floods, respectively. These results may be a useful for future planning and management of estuarine systems given that the common goby is an important species of estuarine food webs in many temperate ecosystems.

Phytoplankton community-level bio-optical assessment in a naturally mercury contaminated Antarctic ecosystem (Deception Island).

Mercury naturally contaminated environments, like Deception Island (Antarctica), are field labs to study the physiological consequences of chronic Hg-exposure at the community level. Deception Island volcanic vents lead to a continuous chronic exposure of the phytoplanktonic communities to potentially toxic Hg concentrations. Comparing Hg-contaminated areas (Fumarolas Bay - FB, Gabriel de Castilla station - GdC station), no significant differences in chlorophyll a concentrations were detected, indicating that biomass production was not impaired by Hg-exposure despite the high Hg levels found in the cells. Moreover, the electron transport energy, responsible for energy production, also presented rather similar values in phytoplankton from both locations. Regarding FB communities, although the cells absorbed and trapped lower amounts of energy, the effect of Hg was not relevant in the photochemical work produced by the electronic transport chain. This might be due to the activation of alternative internal electron donors, as counteractive measure to the energy accumulated inside the cells. In fact, this alternative electron pathway, may have allowed FB communities to have similar electron transport energy fluxes without using respiration as photoprotective measure towards excessive energy. Hg-exposed cells also showed a shift from the energy flux towards the PS I (photosystem I), alleviating the excessive energy accumulation at the PS II (photosystem II) and preventing an oxidative burst. Our findings suggest a higher energy use efficiency in the communities exposed to volcanic Hg, which is not observable in cultured phytoplankton species grown under Hg exposure. This may constitute a metabolic adaptation, driven from chronic exposure allowing the maintenance of high levels of primary productivity under the assumingly unfavourable conditions of Deception Island.

Leaf fatty acid remodeling in the salt-excreting halophytic grass Spartina patens along a salinity gradient.

Spartina patens is a highly dispersed halophytic grass invader in Mediterranean marshes. It is also characterized by having a high degree of resistance to salinity, one of the main drivers of plant zonation in salt marshes. Nevertheless, the physiological basis behind the extreme resistance of S. patens requires more detailed studies. In the present work, we aimed to study how membrane fatty acid remodeling could contribute to the resistance of this plant to salt. Spartina patens individuals exposed to increasing levels of salinity and its leaf fatty acid profile under lipid peroxidation products evaluated under all tested concentrations. A significant increase in the relative amounts of the saturated fatty acids (SFA) was observed, namely palmitic acid (C16:0), essential for PS II functioning, and stearic (C18:0) acid. The chloroplastidial trans-hexadecenoic acid (C16:1t) as well as the polyunsaturated linoleic (C18:2) and linolenic (C18:3) acids showed significant decreases in all the salt treatments. These changes led to a reduction in the double bond index in salt-treated plants which reflects reduction of the fluidity of the chloroplast membranes, which could contribute to maintain the membrane impermeable to the toxic exogenous Na. Despite the decrease observed in the total fatty acid contents in plants exposed to high salt concentrations the amounts of lipid peroxidation products decreased highlighting the resistance of this species towards toxic exogenous salt concentrations. Membrane fatty acid remodeling could represent an efficient mechanism to maintain the photosynthetic machinery of S. patens highly efficient under salt stress.

Atmospheric CO2 enrichment effect on the Cu-tolerance of the C4 cordgrass Spartina densiflora.

A glasshouse experiment was designed to investigate the effect of the co-occurrence of 400 and 700ppm CO2 at 0, 15 and 45mM Cu on the Cu-tolerance of C4 cordgrass species Spartina densiflora, by measuring growth, gas exchange, efficiency of PSII, pigments profiles, antioxidative enzyme activities and nutritional balance. Our results revealed that the rising atmospheric CO2 mitigated growth reduction imposed by Cu in plants grown at 45mM Cu, leading to leaf Cu concentration bellow than 270mgKg-1 Cu, caused by an evident dilution effect. On the other hand, non-CO2 enrichment plants showed leaf Cu concentration values up to 737.5mgKg-1 Cu. Furthermore, improved growth was associated with higher net photosynthetic rate (AN). The beneficial effect of rising CO2 on photosynthetic apparatus seems to be associated with a reduction of stomatal limitation imposed by Cu excess, which allowed these plants to maintain greater iWUE values. Also, plants grown at 45mM Cu and 700ppm CO2, showed higher ETR values and lower energy dissipation, which could be linked with an induction of Rubisco carboxylation and supported by the recorded amelioration of N imbalance. Furthermore, higher ETR values under CO2 enrichment could lead to an additional consumption of reducing equivalents. Idea that was reflected in the lower values of ETRmax/AN ratio, malondialdehyde (MDA) and ascorbate peroxidase (APx), guaiacol peroxidase (GPx) and superoxide dismutase (SOD) activities under Cu excess, which could indicate a lower production of ROS species under elevated CO2 concentration, due to a better use of absorbed energy.

Compliance of secondary production and eco-exergy as indicators of benthic macroinvertebrates assemblages' response to canopy cover conditions in Neotropical headwater streams.

Riparian vegetation cover influences benthic assemblages structure and functioning in headwater streams, as it regulates light availability and autochthonous primary production in these ecosystems.Secondary production, diversity, and exergy-based indicators were applied in capturing how riparian cover influences the structure and functioning of benthic macroinvertebrate assemblages in tropical headwater streams. Four hypotheses were tested: (1) open canopy will determine the occurrence of higher diversity in benthic macroinvertebrate assemblages; (2) streams with open canopy will exhibit more complex benthic macroinvertebrate communities (in terms of information embedded in the organisms' biomass); (3) in streams with open canopy benthic macroinvertebrate assemblages will be more efficient in using the available resources to build structure, which will be reflected by higher eco-exergy values; (4) benthic assemblages in streams with open canopy will exhibit more secondary productivity. We selected eight non-impacted headwater streams, four shaded and four with open canopy, all located in the Neotropical savannah (Cerrado) of southeastern Brazil. Open canopy streams consistently exhibited significantly higher eco-exergy and instant secondary production values, exemplifying that these streams may support more complex and productive benthic macroinvertebrate assemblages. Nevertheless, diversity indices and specific eco-exergy were not significantly different in shaded and open canopy streams. Since all the studied streams were selected for being considered as non-impacted, this suggests that the potential represented by more available food resources was not used to build a more complex dissipative structure. These results illustrate the role and importance of the canopy cover characteristics on the structure and functioning of benthic macroinvertebrate assemblages in tropical headwater streams, while autochthonous production appears to play a crucial role as food source for benthic macroinvertebrates. This study also highlights the possible application of thermodynamic based indicators as tools to guide environmental managers in developing and implementing policies in the neotropical savannah.